1. Field of the Invention
The present invention relates to coupling arrangement including an optical photoconductive drum and a grounding plate in an electro-photographic machine, and more particularly, to the grounding plate that can remove an electrically resistive coating from an interior of the drum to achieve electrical connection therewith, and/or to the grounding plate and a flange, in combination, that can achieve an interference fit with the drum.
2. Discussion of the Related Art
In a known electro-photographic machine, such as a copier, a laser printer, a facsimile, and the like, a known process cartridge is removably mounted to a known main assembly.
The main assembly includes, among other components, a housing, a control panel disposed within the housing for controlling an image forming process, an electronic control system that is operated by the control panel, a motor that is controlled by the control system, a gear train that is driven by the motor, and electrical contacts for delivering power to the removable process cartridge that is inserted into and retained within grooves or channels formed in opposing side walls of the housing. The main assembly also includes an optical projection system and a central processor that controls a sequence and a timing of the optical projection system during a known image forming operation.
The removable process cartridge includes, among other components, an optical photoconductive drum (OPC drum), and a driving gear for driving one or more components of the process cartridge, such as a charging device, a developing device, a cleaning device, and the like.
During the known image forming operation, the OPC drum undergoes a charging/discharging cycle to create a developer image (i.e., a toner image) on a recording material (e.g., a sheet of paper, a transparent sheet, etc.). Briefly, during the charging cycle, the charging device uniformly charges an exterior surface of the OPC drum. The optical projection system projects image containing information in the form of a laser light to selectively discharge a portion of the exterior surface of the OPC drum, thereby forming a latent image. The developing device applies the developer or toner to the partially charged exterior surface of the OPC drum. The toner is electro-statically attracted to the charged areas of the OPC drum, thereby forming a toner image. The toner image is then transferred from the exterior surface of the OPC drum to the sheet of paper.
In the known electro-photographic machine, the exterior surface of the OPC drum is coated with an electrically resistive coating to improve a quality of the image produced during the image forming process. Examples of known electrically resistive coatings include hard anodization with aluminum oxide (Al2O3), oxidized surfaces, and the like. The OPC drum is submerged in the electrically resistive coating, such that an interior surface of the OPC drum is coated with the electrically resistive coating as well as the exterior surface.
It is also known that the coated OPC drum must be sufficiently grounded to undergo the required discharging portion of the charging/discharging cycle. In the known grounding or earthing arrangement, a grounding plate is disposed beneath the driving gear and within an interior portion of the OPC drum. The grounding plate includes a plurality of radially extending projections that contact the interior surface of the OPC drum. However, to satisfactorily ground the OPC drum, a portion of the electrically resistive coating must be removed through a separate and/or additional process such that the projections of the grounding plate can achieve electrical connection with the interior surface of the OPC drum. An example of a known process for removal of the electrically resistive coating includes a laser scribing operation. The grounding plate also includes a second plurality of projections that contact an electrically conductive shaft extending through the driving gear. After the grounding plate is aligned and inserted into the OPC drum, the driving gear is secured to the drum by a separate and/or additional securing means, thereby preventing relative movement and/or rotation of the grounding plate to the OPC drum. An example of a known securing means includes an adhesive. By this arrangement, the OPC drum is grounded through the grounding plate and/or the shaft.
However, the conventional grounding arrangement suffers from a number of disadvantages. For example, as stated above, the radially extending projections of the grounding plate must be precisely aligned with the portions of the interior surface of the OPC drum from which the electrically resistive coating has been removed to satisfactorily ground the OPC drum. The requirement for such precise alignment provides an impediment to an automatic assembly of the known process cartridge. Further, the resistive coating must be removed from the interior surface of the OPC drum by a separate and/or additional process. Further, the known process cartridge requires additional securing means between the OPC drum and the driving gear to prevent relative movement and/or rotation therebetween. The use of the adhesive as the securing means requires that care be taken to prevent the relative rotation and/or movement after insertion of the grounding plate and the driving gear into the OPC drum before curing of the adhesive. Such disadvantages increase the manufacturing time and/or cost of the known process cartridge.
The present invention provides a coupling arrangement with an optical photoconductive drum including a drum exterior surface and a drum interior surface having an electrically resistive coating surrounding and extending along a longitudinal axis. The drum interior surface faces toward the longitudinal axis and the drum exterior surface faces away from the longitudinal axis. The drum interior surface includes first and second open ends. A gear flange including a gear interior surface is disposed in the first open end. A gear exterior surface is disposed outside of the first open end. A gear side surface connects the gear interior and exterior surfaces. A grounding shaft opening extends between the gear interior and exterior surfaces. A grounding plate is disposed in the first open end and includes an outwardly extending contact that contacts the drum interior surface and removes a portion of the electrically resistive coating to achieve electrical connection with the drum interior surface and to hold the flange.
The present invention provides a method of grounding an optical photoconductive drum including a drum exterior surface and a drum interior surface having an electrically resistive coating surrounding and extending along a longitudinal axis, the drum interior surface including first and second open ends. A portion of the electrically resistive coating is removed with a first protrusion of a grounding plate to electrically connect the drum interior surface and the grounding plate. A grounding shaft is contacted with a second protrusion of the grounding plate to electrically connect the grounding shaft and the grounding plate.
The present invention provides a method of assembling a drum assembly with an optical photoconductive drum including a drum exterior surface and a drum interior surface having an electrically resistive coating surrounding and extending along a longitudinal axis, the drum interior surface defining first and second open ends. A gear flange is inserted in the first open end. A grounding plate including a first and a second protrusion is inserted in the first open end, the first protrusion achieving an interference fit with the drum interior surface. A grounding shaft is inserted into an opening in the gear flange, the grounding shaft achieving an interference fit with the second protrusion of the grounding plate.